/******************************************************
Server query execution

(c) 1996 Innobase Oy

Created 6/5/1996 Heikki Tuuri
*******************************************************/

#include "srv0que.h"

#include "srv0srv.h"
#include "sync0sync.h"
#include "os0thread.h"
#include "usr0sess.h"
#include "que0que.h"

/**************************************************************************
Checks if there is work to do in the server task queue. If there is, the
thread starts processing a task. Before leaving, it again checks the task
queue and picks a new task if any exists. This is called by a SRV_WORKER
thread. */

void srv_que_task_queue_check(void)
/*==========================*/
{
  que_thr_t *thr;

  for (;;)
  {
    mutex_enter(&kernel_mutex);

    thr = UT_LIST_GET_FIRST(srv_sys->tasks);

    if (thr == NULL)
    {
      mutex_exit(&kernel_mutex);

      return;
    }

    UT_LIST_REMOVE(queue, srv_sys->tasks, thr);

    mutex_exit(&kernel_mutex);

    que_run_threads(thr);
  }
}

/**************************************************************************
Performs round-robin on the server tasks. This is called by a SRV_WORKER
thread every second or so. */

que_thr_t *srv_que_round_robin(
    /*================*/
    /* out: the new (may be == thr) query thread
    to run */
    que_thr_t *thr) /* in: query thread */
{
  que_thr_t *new_thr;

  ut_ad(thr);
  ut_ad(thr->state == QUE_THR_RUNNING);

  mutex_enter(&kernel_mutex);

  UT_LIST_ADD_LAST(queue, srv_sys->tasks, thr);

  new_thr = UT_LIST_GET_FIRST(srv_sys->tasks);

  mutex_exit(&kernel_mutex);

  return (new_thr);
}

/**************************************************************************
Enqueues a task to server task queue and releases a worker thread, if there
is a suspended one. */

void srv_que_task_enqueue_low(
    /*=====================*/
    que_thr_t *thr) /* in: query thread */
{
  ut_ad(thr);

#ifdef UNIV_SYNC_DEBUG
  ut_ad(mutex_own(&kernel_mutex));
#endif /* UNIV_SYNC_DEBUG */

  UT_LIST_ADD_LAST(queue, srv_sys->tasks, thr);

  srv_release_threads(SRV_WORKER, 1);
}

/**************************************************************************
Enqueues a task to server task queue and releases a worker thread, if there
is a suspended one. */

void srv_que_task_enqueue(
    /*=================*/
    que_thr_t *thr) /* in: query thread */
{
  ut_ad(thr);

  ut_a(0); /* Under MySQL this is never called */

  mutex_enter(&kernel_mutex);

  srv_que_task_enqueue_low(thr);

  mutex_exit(&kernel_mutex);
}
